Method of placing an implantable device proximate to neural/muscular tissue

ABSTRACT

A method for facilitating placement of an implantable device configured for implantation beneath a patient&#39;s skin for the purpose of tissue, e.g., nerve or muscle, stimulation and/or parameter monitoring and/or data communication. A placement structure is shown for facilitating placement of the implantable device proximate to neural/muscular tissue.

BACKGROUND OF THE INVENTION

The present invention relates to systems for monitoring and/or affectingparameters of a patient's body for the purpose of medical diagnosisand/or treatment. More particularly, systems in accordance with theinvention are characterized by a plurality of devices, preferablybattery-powered, configured for implanting within a patient's body, eachdevice being configured to sense a body parameter, e.g., temperature, O₂content, physical position, etc., and/or to affect a parameter, e.g.,via nerve stimulation.

Applicants' commonly assigned U.S. patent application Ser. No.09/030,106 entitled “Battery Powered Patient Implantable Device”, nowU.S. Pat. No. 6,185,452, incorporated herein by reference, describesdevices configured for implantation within a patient's body, i.e.,beneath a patient's skin, for performing various functions including:(1) stimulation of body tissue, (2) sensing of body parameters, and (3)communicating between implanted devices and devices external to apatient's body.

SUMMARY OF THE INVENTION

The present invention is directed to a system for monitoring and/oraffecting parameters of a patient's body and more particularly to such asystem comprised of a system control unit (SCU) and one or more devicesimplanted in the patient's body, i.e., within the envelope defined bythe patient's skin. Each said implanted device is configured to bemonitored and/or controlled by the SCU via a wireless communicationchannel.

In accordance with the invention, the SCU comprises a programmable unitcapable of (1) transmitting commands to at least some of a plurality ofimplanted devices and (2) receiving data signals from at least some ofthose implanted devices. In accordance with a preferred embodiment, thesystem operates in a closed loop fashion whereby the commandstransmitted by the SCU are dependent, in part, on the content of thedata signals received by the SCU.

In accordance with a preferred embodiment, each implanted device isconfigured similarly to the devices described in Applicants' commonlyassigned U.S. patent application Ser. No. 09/030,106, now U.S. Pat. No.6,185,452, and typically comprises a sealed housing suitable forinjection into the patient's body. Each housing preferably contains apower source having a capacity of at least 1 microwatt-hour, preferablya rechargeable battery, and power consuming circuitry preferablyincluding a data signal transmitter and receiver and sensor/stimulatorcircuitry for driving an input/output transducer.

In accordance with a significant aspect of the preferred embodiment, apreferred SCU is also implemented as a device capable of being injectedinto the patient's body. Wireless communication between the SCU and theother implanted devices can be implemented in various ways, e.g., via amodulated sound signal, AC magnetic field, RF signal, or electricalconduction.

In accordance with a further aspect of the invention, the SCU isremotely programmable, e.g., via wireless means, to interact with theimplanted devices according to a treatment regimen. In accordance with apreferred embodiment, the SCU is preferably powered via an internalpower source, e.g., a rechargeable battery. Accordingly, an SCU combinedwith one or more battery-powered implantable devices, such as thosedescribed in the commonly assigned U.S. Pat. No. 6,185,452, form aself-sufficient system for treating a patient.

In accordance with a preferred embodiment, the SCU and other implanteddevices are implemented substantially identically, being comprised of asealed housing configured to be injected into the patient's body. Eachhousing contains sensor/stimulator circuitry for driving an input/outputtransducer, e.g., an electrode, to enable it to additionally operate asa sensor and/or stimulator.

Alternatively, the SCU could be implemented as an implantable butnon-injectable housing which would permit it to be physically largerenabling it to accommodate larger, higher capacity components, e.g., abattery, microcontroller, etc. As a further alternative, the SCU couldbe implemented in a housing configured for carrying on the patient'sbody outside of the skin defined envelope, e.g., in a wrist band.

In accordance with the invention, the commands transmitted by the SCUcan be used to remotely configure the operation of the other implanteddevices and/or to interrogate the status of those devices. For example,various operating parameters, e.g., the pulse frequency, pulse width,trigger delays, etc., of each implanted device can be controlled orspecified in one or more commands addressably transmitted to the device.Similarly, the sensitivity of the sensor circuitry and/or theinterrogation of a sensed parameter, e.g., battery status, can beremotely specified by the SCU.

In accordance with a significant feature of the preferred embodiment,the SCU and/or each implantable device includes a programmable memoryfor storing a set of default parameters. In the event of power loss, SCUfailure, or any other catastrophic occurrence, all devices default tothe safe harbor default parameters. The default parameters can beprogrammed differently depending upon the condition being treated. Inaccordance with a further feature, the system includes a switch,preferably actuatable by an external DC magnetic field, for resettingthe system to its default parameters.

In an exemplary use of a system in accordance with the presentinvention, a patient with nerve damage can have a damaged nerve“replaced” by an implanted SCU and one or more implanted sensors andstimulators, each of which contains its own internal power source. Inthis exemplary system, the SCU would monitor a first implanted sensorfor a signal originating from the patient's brain and responsivelytransmit command signals to one or more stimulators implanted past thepoint of nerve damage. Furthermore, the SCU could monitor additionalsensors to determine variations in body parameters and, in a closed loopmanner, react to control the command signals to achieve the desiredtreatment regimen.

In a further aspect of a preferred embodiment of the present invention,a placement structure is shown for facilitating placement of animplantable device having at least two electrodes proximate toneural/muscular tissue, wherein the placement structure comprises (1) aholder having a hollow cavity formed within for holding and retainingthe implantable device within; (2) at least one set of elastic wings forcapturing neural/muscular tissue; and wherein the placement structure isprimarily formed from a biocompatible plastic.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will be best understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of the system of the presentinvention comprised of implanted devices, e.g., microstimulators,microsensors and microtransponders, under control of an implanted systemcontrol unit (SCU).

FIG. 2 comprises a block diagram of the system of FIG. 1 showing thefunctional elements that form the system control unit and implantedmicrostimulators, microsensors and microtransponders.

FIG. 3A comprises a block diagram of an exemplary implanted device, asshown in the commonly assigned U.S. Pat. No. 6,185,452, including abattery for powering the device for a period of time in excess of onehour in response to a command from the system control unit.

FIG. 3B comprises a simplified block diagram of controller circuitrythat can be substituted for the controller circuitry of FIG. 3A, thuspermitting a single device to be configured as a system control unitand/or a microstimulator and/or a microsensor and/or a microtransponder.

FIG. 4 is a simplified diagram showing the basic format of data messagesfor commanding/interrogating the implanted microstimulators,microsensors and microtransponders which form a portion of the presentinvention.

FIG. 5 shows an exemplary flow chart of the use of the present system inan open loop mode for controlling/monitoring a plurality of implanteddevices, e.g., microstimulators, microsensors.

FIG. 6 shows a flow chart of the optional use of a translation table forcommunicating with microstimulators and/or microsensors viamicrotransponders.

FIG. 7 shows a simplified flow chart of the use of closed loop controlof a microstimulator by altering commands from the system control unitin response to status data received from a microsensor.

FIG. 8 shows an exemplary injury, i.e., a damaged nerve, and theplacement of a plurality of implanted devices, i.e., microstimulators,microsensors and a microtransponder under control of the system controlunit for “replacing” the damaged nerve.

FIG. 9 shows a simplified flow chart of the control of the implanteddevices of FIG. 8 by the system control unit.

FIG. 10A shows a side view of a battery-powered implanted device, e.g.,a microstimulator, made in accordance with the present invention.

FIG. 10B shows a side view of another implantable battery-powereddevice, one employing an internal coupling capacitor, made in accordancewith the invention.

FIGS. 10C and 10D show two side cutaway views of the presently preferredembodiment of an implantable ceramic tube suitable for housing thesystem control unit and/or microstimulators and/or microsensors and/ormicrotransponders.

FIG. 11 illustrates an exemplary battery suitable for powering theimplantable devices which comprise the components of the presentinvention.

FIG. 12 shows an exemplary housing suitable for an implantable SCUhaving a battery enclosed within that has a capacity of at least 1watt-hour.

FIG. 13 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 14 is a cross-sectional view of the housing of FIG. 13 taken alongline 14-14.

FIG. 15 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 16 is a cross-sectional view of the housing of FIG. 15 taken alongline 16-16.

FIG. 17 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 18 is a cross-sectional view of the housing of FIG. 17 taken alongline 18-18.

FIG. 19 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 20 is a cross-sectional view of the housing of FIG. 19 taken alongline 20-20.

FIG. 21 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 22 is a cross-sectional view of the housing of FIG. 21 taken alongline 22-22.

FIG. 23 is an alternative embodiment of the housing of FIGS. 10A-10D.

FIG. 24 is a cross-sectional view of the housing of FIG. 23 taken alongline 24-24.

FIG. 25 is a perspective view of an exemplary placement structure of thepresent invention which is formed for holding one of the aforementionedimplantable device in close proximity to a nerve, muscle tissue, or thelike.

FIG. 26 is a perspective view of the placement structure of FIG. 25having one of the aforementioned placement devices held within a hollowcavity within its holder portion.

FIG. 27 is a perspective view of the placement structure of FIGS. 25 and26 showing its wings capturing neural/muscular tissue.

FIG. 28 is an end view of the placement structure of FIGS. 25 and 26.

FIG. 29 is an end view of the placement structure of FIGS. 25 and 26having hooks at the ends of its wings for providing additional means forretaining the placement structure in close proximity to theneural/muscular tissue.

FIG. 30 is an exemplary laparoscopic device suitable for implanting theplacement structure of the present invention which in turn is holdingone of the aforementioned implantable devices in close proximity toneural/muscular tissue.

FIG. 31 is a cross sectional view of that shown in FIG. 30 along theline 31-31 wherein the wings of the placement structure have been foldedinward toward the implantable device before insertion, e.g., via itstip, into the hollow portion of the laparoscopic device.

FIG. 32 is a cross sectional view of that shown in FIG. 27 along theline 32-32 showing the wings of the placement structure holdingneural/muscular tissue and the resulting stimulation/sensing vectors.

FIG. 33 is an alternative embodiment of the placement structure of FIG.25 wherein inner portions of the wings and the cavity include conductivelayers (preferably a plurality of conductive paths) to provideadditional electrical coupling between the electrodes of the implantabledevice axially along the neural/muscular tissue.

FIG. 34 is a next alternative embodiment of the placement structure ofFIG. 25 wherein inner portions of the wings and the cavity includeconductive layers (preferably a plurality of conductive paths) toprovide additional electrical coupling between the electrodes of theimplantable device transversely across the neural/muscular tissue usinga pair of wings.

FIG. 35 is an alternative embodiment of the placement structure of FIG.25 and the implantable medical device of FIGS. 10A-10D wherein theimplantable medical device additionally includes a plurality ofstimulator/sensor circuitry portions that are coupled via a plurality ofelectrode connectors and a plurality of conductive paths to innerportions of the wings and the cavity of the placement structure toprovide stimulation to or sensing from displaced portions of theneural/muscular tissue.

FIG. 36 shows an alternative implementation of that which isfunctionally described in relation to FIG. 35. However, in thisimplementation a single, essentially U-shaped, structure having elasticwings is integrally formed which encompasses the functionality of theimplantable medical device of FIGS. 10A-10D contained within theplacement structure.

FIG. 37 shows a next alternative implementation of that which isfunctionally described in relation to FIGS. 35 and 36 to the extent thatit too is an integral device but it has its elastic wings 504 formedfrom a silicone rubber impregnated cloth that is permanently attached tothe functional equivalent of the implantable medical device which wasdescribed in reference to FIGS. 10A-10D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a system for monitoring and/oraffecting parameters of a patient's body and more particularly to such asystem comprised of a system control unit (SCU) and one or more devicesimplanted in a patient's body, i.e., within the envelope defined by thepatient's skin. Each such implantable device is configured to bemonitored and/or controlled by the SCU via a wireless communicationchannel.

In accordance with the invention, the SCU comprises a programmable unitcapable of (1) transmitting commands to at least some of a plurality ofimplanted devices and (2) receiving data signals from at least some ofthose implanted devices. In accordance with a preferred embodiment, thesystem operates in closed loop fashion whereby the commands transmittedby the SCU are dependent, in part, on the content of the data signalsreceived by the SCU.

In accordance with a preferred embodiment, each implanted device isconfigured similarly to the devices described in Applicants' commonlyassigned U.S. patent application Ser. No. 09/030,106, now U.S. Pat. No.6,185,452, and typically comprises a sealed housing suitable forinjection into the patient's body. Each housing preferably contains apower source having a capacity of at least 1 microwatt-hour, preferablya rechargeable battery, and power consuming circuitry preferablyincluding a data signal transmitter and receiver and sensor/stimulatorcircuitry for driving an input/output transducer.

FIG. 1 (essentially corresponding to FIG. 2 of the commonly assignedU.S. Pat. No. 6,185,452) and FIG. 2 show an exemplary system 300 made ofimplanted devices 100, preferably battery powered, under control of asystem control unit (SCU) 302, preferably also implanted beneath apatient's skin 12. As described in the commonly assigned U.S. Pat. No.6,185,452, potential implanted devices 100 (see also the block diagramshown in FIG. 3A) include stimulators, e.g., 100 a, sensors, e.g., 100c, and transponders, e.g., 100 d. Such stimulators, e.g., 100 a, can beremotely programmed to output a sequence of drive pulses to body tissueproximate to its implanted location via attached electrodes. Thesensors, e.g., 100 c, can be remotely programmed to sense one or morephysiological or biological parameters in the implanted environment ofthe device, e.g., temperature, glucose level, O₂ content, etc.Transponders, e.g., 100 d, are devices which can be used to extend theinterbody communication range between stimulators and sensors and otherdevices, e.g., a clinician's programmer 172 and a patient control unit174. Preferably, these stimulators, sensors and transponders arecontained in sealed elongate housing having an axial dimension of lessthan 60 mm and a lateral dimension of less than 6 mm. Accordingly, suchstimulators, sensors and transponders are respectively referred to asmicrostimulators, microsensors, and microtransponders. Suchmicrostimulators and microsensors can thus be positioned beneath theskin within a patient's body using a hypodermic type insertion tool 176.

As described in the commonly assigned U.S. Pat. No. 6,185,452,microstimulators and microsensors are remotely programmed andinterrogated via a wireless communication channel, e.g., modulated ACmagnetic, sound (i.e., ultrasonic), RF or electric fields, typicallyoriginating from control devices external to the patient's body, e.g., aclinician's programmer 172 or patient control unit 174. Typically, theclinician's programmer 172 is used to program a single continuous or onetime pulse sequence into each microstimulator and/or measure abiological parameter from one or more microsensors. Similarly, thepatient control unit 174 typically communicates with the implanteddevices 100, e.g., microsensors 100 c, to monitor biological parameters.In order to distinguish each implanted device over the communicationchannel, each implanted device is manufactured with an identificationcode (ID) 303 specified in address storage circuitry 108 (see FIG. 3A)as described in the commonly assigned U.S. Pat. No. 6,185,452.

By using one or more such implantable devices in conjunction with theSCU 302 of the present invention, the capabilities of such implanteddevices can be further expanded. For example, in an open loop mode(described below in reference to FIG. 5), the SCU 302 can be programmedto periodically initiate tasks, e.g., perform real time tasking, such astransmitting commands to microstimulators according to a prescribedtreatment regimen or periodically monitor biological parameters todetermine a patient's status or the effectiveness of a treatmentregimen. Alternatively, in a closed loop mode (described below inreference to FIGS. 7-9), the SCU 302 periodically interrogates one ormore microsensors and accordingly adjust the commands transmitted to oneor more microstimulators.

FIG. 2 shows the system 300 of the present invention comprised of (1)one or more implantable devices 100 operable to sense and/or stimulate apatient's body parameter in accordance with one or more controllableoperating parameters and (2) the SCU 302. The SCU 302 is primarilycomprised of (1) a housing 206, preferably sealed and configured forimplantation beneath the skin of the patient's body as described in thecommonly assigned U.S. Pat. No. 6,185,452 in reference to the implanteddevices 100, (2) a signal transmitter 304 in the housing 206 fortransmitting command signals, (3) a signal receiver 306 in the housing206 for receiving status signals, and (4) a programmable controller 308,e.g., a microcontroller or state machine, in the housing 206 responsiveto received status signals for producing command signals fortransmission by the signal transmitter 304 to other implantable devices100. The sequence of operations of the programmable controller 308 isdetermined by an instruction list, i.e., a program, stored in programstorage 310, coupled to the programmable controller 308. While theprogram storage 310 can be a nonvolatile memory device, e.g., ROM,manufactured with a program corresponding to a prescribed treatmentregimen, it is preferable that at least a portion of the program storage310 be an alterable form of memory, e.g., RAM, EEPROM, etc., whosecontents can be remotely altered as described further below. However, itis additionally preferable that a portion of the program storage 310 benonvolatile so that a default program is always present. The rate atwhich the program contained within the program storage 310 is executedis determined by clock 312, preferably a real time clock that permitstasks to be scheduled at specified times of day.

The signal transmitter 304 and signal receiver 306 preferablycommunicate with implanted devices 100 using sound means, i.e.,mechanical vibrations, using a transducer having a carrier frequencymodulated by a command data signal. In a preferred embodiment, a carrierfrequency of 100 KHz is used which corresponds to a frequency thatfreely passes through a typical body's fluids and tissues. However, suchsound means that operate at any frequency, e.g., greater than 1 Hz, arealso considered to be within the scope of the present invention.Alternatively, the signal transmitter 304 and signal receiver 306 cancommunicate using modulated AC magnetic, RF, or electric fields.

The clinician's programmer 172 and/or the patient control unit 174and/or other external control devices can also communicate with theimplanted devices 100, as described in the commonly assigned U.S. Pat.No. 6,185,452, preferably using a modulated AC magnetic field.Alternatively, such external devices can communicate with the SCU 302via a transceiver 314 coupled to the programmable controller 308. Since,in a preferred operating mode, the signal transmitter 304 and signalreceiver 306 operate using sound means, a separate transceiver 314 whichoperates using magnetic means is used for communication with externaldevices. However, a single transmitter 304/receiver 306 can be used inplace of transceiver 314 if a common communication means is used.

FIG. 3A comprises a block diagram of an exemplary implanted device 100(as shown in FIG. 2 of the commonly assigned U.S. Pat. No. 6,185,452)which includes a battery 104, preferably rechargeable, for powering thedevice for a period of time in excess of one hour and responsive tocommand signals from a remote device, e.g., the SCU 302. As described inthe commonly assigned U.S. Pat. No. 6,185,452, the implantable device100 is preferably configurable to alternatively operate as amicrostimulator and/or microsensor and/or microtransponder due to thecommonality of most of the circuitry contained within. Such circuitrycan be further expanded to permit a common block of circuitry to alsoperform the functions required for the SCU 302. Accordingly, FIG. 3Bshows an alternative implementation of the controller circuitry 106 ofFIG. 3A that is suitable for implementing a microstimulator and/or amicrosensor and/or a microtransponder and/or the SCU 302. In thisimplementation, configuration data storage 132 can be alternatively usedas the program storage 310 when the implantable device 100 is used asthe SCU 302. In this implementation, XMTR 168 corresponds to the signaltransmitter 304 and a RCVR 114 b corresponds to the signal receiver 306(preferably operable using sound means via transducer 138) and the RCVR114 a and XMTR 146 correspond to the transceiver 314 (preferablyoperable using magnetic means via coil 116).

In a preferred embodiment, the contents of the program storage 310,i.e., the software that controls the operation of the programmablecontroller 308, can be remotely downloaded, e.g., from the clinician'sprogrammer 172 using data modulated onto an AC magnetic field. In thisembodiment, it is preferable that the contents of the program storage310 for each SCU 302 be protected from an inadvertent change.Accordingly, the contents of the address storage circuitry 108, i.e.,the ID 303, is preferably used as a security code to confirm that thenew program storage contents are destined for the SCU 302 receiving thedata. This feature is significant if multiple patient's could bephysically located, e.g., in adjoining beds, within the communicationrange of the clinician's programmer 172.

In a further aspect of the present invention, it is preferable that theSCU 302 be operable for an extended period of time, e.g., in excess ofone hour, from an internal power supply 316. While a primary battery,i.e., a nonrechargeable battery, is suitable for this function, it ispreferable that the power supply 316 include a rechargeable battery,e.g., battery 104 as described in the commonly assigned U.S. Pat. No.6,185,452, that can be recharged via an AC magnetic field producedexternal to the patient's body. Accordingly, the power supply 102 ofFIG. 3A (described in detail in the commonly assigned U.S. Pat. No.6,185,452) is the preferred power supply 316 for the SCU 302 as well.

The battery-powered devices 100 of the commonly assigned U.S. Pat. No.6,185,642 are preferably configurable to operate in a plurality ofoperation modes, e.g., via a communicated command signal. In a firstoperation mode, device 100 is remotely configured to be amicrostimulator, e.g., 100 a and 100 b. In this embodiment, controller130 commands stimulation circuitry 110 to generate a sequence of drivepulses through electrodes 112 to stimulate tissue, e.g., a nerve,proximate to the implanted location of the microstimulator, e.g., 100 aor 100 b. In operation, a programmable pulse generator 178 and voltagemultiplier 180 are configured with parameters (see Table I)corresponding to a desired pulse sequence and specifying how much tomultiply the battery voltage (e.g., by summing charged capacitors orsimilarly charged battery portions) to generate a desired compliancevoltage V_(c). A first FET 182 is periodically energized to store chargeinto capacitor 183 (in a first direction at a low current flow ratethrough the body tissue) and a second FET 184 is periodically energizedto discharge capacitor 183 in an opposing direction at a higher currentflow rate which stimulates a nearby nerve. Alternatively, electrodes canbe selected that will form an equivalent capacitor within the bodytissue.

TABLE I Stimulation Parameters Current: continuous current charging ofstorage capacitor Charging currents: 1, 3, 10, 30, 100, 250, 500 μaCurrent Range: 0.8 to 40 ma in nominally 3.2% steps Compliance Voltage:selectable, 3-24 volts in 3 volt steps Pulse Frequency (PPS): 1 to 5000PPS in nominally 30% steps Pulse Width: 5 to 2000 μs in nominally 10%steps Burst On Time (BON): 1 ms to 24 hours in nominally 20% steps BurstOff Time (BOF): 1 ms to 24 hours in nominally 20% steps Triggered Delayto BON: either selected BOF or pulse width Burst Repeat Interval: 1 msto 24 hours in nominally 20% steps Ramp On Time: 0.1 to 100 seconds (1,2, 5, 10 steps) Ramp Off Time: 0.1 to 100 seconds (1, 2, 5, 10 steps)

In a next operation mode, the battery-powered implantable device 100 canbe configured to operate as a microsensor, e.g., 100 c, that can senseone or more physiological or biological parameters in the implantedenvironment of the device. In accordance with a preferred mode ofoperation, the system control unit 302 periodically requests the senseddata from each microsensor 100 c using its ID stored in address storagecircuitry 108, and responsively sends command signals tomicrostimulators, e.g., 100 a and 100 b, adjusted accordingly to thesensed data. For example, sensor circuitry 188 can be coupled to theelectrodes 112 to sense or otherwise used to measure a biologicalparameter, e.g., temperature, glucose level, or O₂ content and providedthe sensed data to controller circuitry 106. Preferably, the sensorcircuitry includes a programmable bandpass filter and an analog todigital (A/D) converter that can sense and accordingly convert thevoltage levels across the electrodes 112 into a digital quantity.Alternatively, the sensor circuitry can include one or more senseamplifiers to determine if the measured voltage exceeds a thresholdvoltage value or is within a specified voltage range. Furthermore, thesensor circuitry 188 can be configurable to include integrationcircuitry to further process the sensed voltage. The operation modes ofthe sensor circuitry 188 is remotely programmable via the devicescommunication interface as shown below in Table II.

TABLE II Sensing Parameters Input voltage range: 5 μv to 1 V Bandpassfilter rolloff: 24 dB Low frequency cutoff choices: 3, 10, 30, 100, 300,1000 Hz High frequency cutoff choices: 3, 10, 30, 100, 300, 1000 HzIntegrator frequency choices: 1 PPS to 100 PPS Amplitude threshold 4bits of resolution for detection choices:

Additionally, the sensing capabilities of a microsensor include thecapability to monitor the battery status via path 124 from the chargingcircuit 122 and can additionally include using the ultrasonic transducer138 or the coil 116 to respectively measure the magnetic or ultrasonicsignal magnitudes (or transit durations) of signals transmitted betweena pair of implanted devices and thus determine the relative locations ofthese devices. This information can be used to determine the amount ofbody movement, e.g., the amount that an elbow or finger is bent, andthus form a portion of a closed loop motion control system.

In another operation mode, the battery-powered implantable device 100can be configured to operate as a microtransponder, e.g., 100 d. In thisoperation mode, the microtransponder receives (via the aforementionedreceiver means, e.g., AC magnetic, sonic, RF or electric) a firstcommand signal from the SCU 302 and retransmits this signal (preferablyafter reformatting) to other implanted devices (e.g., microstimulators,microsensors, and/or microtransponders) using the aforementionedtransmitter means (e.g., magnetic, sonic, RF or electric). While amicrotransponder may receive one mode of command signal, e.g., magnetic,it may retransmit the signal in another mode, e.g., ultrasonic. Forexample, clinician's programmer 172 may emit a modulated magnetic signalusing a magnetic emitter 190 to program/command the implanted devices100. However, the magnitude of the emitted signal may not be sufficientto be successfully received by all of the implanted devices 100. Assuch, a microtransponder 100 d may receive the modulated magnetic signaland retransmit it (preferably after reformatting) as a modulatedultrasonic signal which can pass through the body with fewerrestrictions. In another exemplary use, the patient control unit 174 mayneed to monitor a microsensor 100 c in a patient's foot. Despite theefficiency of ultrasonic communication in a patient's body, anultrasonic signal could still be insufficient to pass from a patient'sfoot to a patient's wrist (the typical location of the patient controlunit 174). As such, a microtransponder 100 d could be implanted in thepatient's torso to improve the communication link.

FIG. 4 shows the basic format of an exemplary message 192 forcommunicating with the aforementioned battery-powered devices 100, allof which are preconfigured with an address (ID), preferably unique tothat device, in their address storage circuitry 108 to operate in one ormore of the following modes (1) for nerve stimulation, i.e., as amicrostimulator, (2) for biological parameter monitoring, i.e., as amicrosensor, and/or (3) for retransmitting received signals afterreformatting to other implanted devices, i.e., as a microtransponder.The command message 192 is primarily comprised of a (1) start portion194 (one or more bits to signify the start of the message and tosynchronize the bit timing between transmitters and receivers), (2) amode portion 196 (designating the operating mode, e.g., microstimulator,microsensor, microtransponder, or group mode), (3) an address (ID)portion 198 (corresponding to either the ID in address storage circuitry108 or a programmed group ID), (4) a data field portion 200 (containingcommand data for the prescribed operation), (5) an error checkingportion 202 (for ensuring the validity of the message 192, e.g., by useof a parity bit), and (6) a stop portion 204 (for designating the end ofthe message 192). The basic definition of these fields are shown belowin Table III. Using these definitions, each device can be separatelyconfigured, controlled and/or sensed as part of a system for controllingone or more neural pathways within a patient's body.

TABLE III Message Data Fields MODE ADDRESS (ID) 00 = Stimulator 8 bitidentification address 01 = Sensor 8 bit identification address 02 =Transponder 4 bit identification address 03 = Group 4 bit groupidentification address DATA FIELD PORTION Program/Stimulate = selectoperating mode Parameter/ select programmable parameter inPreconfiguration program mode or preconfigured stimulation Select = orsensing parameter in other modes Parameter Value = program value

Additionally, each device 100 can be programmed with a group ID (e.g., a4 bit value) which is stored in its configuration data storage 132. Whena device 100, e.g., a microstimulator, receives a group ID message thatmatches its stored group ID, it responds as if the message was directedto its ID within its address storage circuitry 108. Accordingly, aplurality of microstimulators, e.g., 100 a and 100 b, can be commandedwith a single message. This mode is of particular use when precisetiming is desired among the stimulation of a group of nerves.

The following describes exemplary commands, corresponding to the commandmessage 192 of FIG. 4, which demonstrate some of the remotecontrol/sensing capabilities of the system of devices which comprise thepresent invention:

Write Command—Set a microstimulator/microsensor specified in the addressfield 198 to the designated parameter value.

Group Write Command—Set the microstimulators/microsensors within thegroup specified in the address field 198 to the designated parametervalue.

Stimulate Command—Enable a sequence of drive pulses from themicrostimulator specified in the address field 198 according topreviously programmed and/or default values.

Group Stimulate Command—Enable a sequence of drive pulses from themicrostimulators within the group specified in the address field 198according to previously programmed and/or default values.

Unit Off Command—Disable the output of the microstimulator specified inthe address field 198.

Group Stimulate Command—Disable the output of the microstimulatorswithin the group specified in the address field 198.

Read Command—Cause the microsensor designated in the address field 198to read the previously programmed and/or default sensor value accordingto previously programmed and/or default values.

Read Battery Status Command—Cause the microsensor designated in theaddress field 198 to return its battery status.

Define Group Command—Cause the microstimulator/microsensor designated inthe address field 198 to be assigned to the group defined in themicrostimulator data field 200.

Set Telemetry Mode Command—Configure the microtransponder designated inthe address field 198 as to its input mode (e.g., AC magnetic, sonic,etc.), output mode (e.g., AC magnetic, sonic, etc.), message length,etc.

Status Reply Command—Return the requested status/sensor data to therequesting unit, e.g., the SCU.

Download Program Command—Download program/safe harbor routines to thedevice, e.g., SCU, microstimulator, etc., specified in the address field198.

FIG. 5 shows a block diagram of an exemplary open loop control program,i.e., a task scheduler 320, for controlling/monitoring a bodyfunction/parameter. In this process, the programmable controller 308 isresponsive to the clock 312 (preferably crystal controlled to thuspermit real time scheduling) in determining when to perform any of aplurality of tasks. In this exemplary flow chart, the programmablecontroller 308 first determines in block 322 if it is now at a timedesignated as T_(EVENT1) (or at least within a sampling error of thattime), e.g., at 1:00 AM. If so, the programmable controller 308transmits a designated command to microstimulator A (ST_(A)) in block324. In this example, the control program continues where commands aresent to a plurality of stimulators and concludes in block 326 where adesignated command is sent to microstimulator X (ST_(X)). Such asubprocess, e.g., a subroutine, is typically used when multiple portionsof body tissue require stimulation, e.g., stimulating a plurality ofmuscle groups in a paralyzed limb to avoid atrophy. The task scheduler320 continues through multiple time event detection blocks until inblock 328 it determines whether the time T_(EVENTM) has arrived. If so,the process continues at block 330 where, in this case, a single commandis sent to microstimulator M (ST_(M)). Similarly, in block 332 the taskscheduler 320 determines when it is the scheduled time, i.e.,T_(EVENTO), to execute a status request from microsensor A (SE_(A)). Ifso, a subprocess, e.g., a subroutine, commences at block 334 where acommand is sent to microsensor A (SE_(A)) to request sensor data and/orspecify sensing criteria. Microsensor A (SE_(A)) does notinstantaneously respond. Accordingly, the programmable controller 308waits for a response in block 336. In block 338, the returned sensorstatus data from microsensor A (SE_(A)) is stored in a portion of thememory, e.g., a volatile portion of the program storage 310, of theprogrammable controller 308. The task scheduler 320 can be a programmedsequence, i.e., defined in software stored in the program storage 310,or, alternatively, a predefined function controlled by a table ofparameters similarly stored in the program storage 310. A similarprocess can be used where the SCU 302 periodically interrogates eachimplantable device 100 to determine its battery status.

FIG. 6 shows an exemplary use of an optional translation table 340 forcommunicating between the SCU 302 and microstimulators, e.g., 100 a,and/or microsensors, e.g., 100 c, via microtransponders, e.g., 100 d. Amicrotransponder, e.g., 100 d, is used when the communication range ofthe SCU 302 is insufficient to reliably communicate with other implanteddevices 100. In this case, the SCU 302 instead directs a data message,i.e., a data packet, to an intermediary microtransponder, e.g., 100 d,which retransmits the data packet to a destination device 100. In anexemplary implementation, the translation table 340 contains pairs ofcorresponding entries, i.e., first entries 342 corresponding todestination addresses and second entries 344 corresponding to theintermediary microtransponder addresses. When the SCU 302 determines,e.g., according to a timed event designated in the program storage 310,that a command is to be sent to a designated destination device (seeblock 346), the SCU 302 searches the first entries 342 of thetranslation table 340, for the destination device address, e.g., ST_(M).The SCU 302 then fetches the corresponding second table entry 344 inblock 348 and transmits the command to that address in block 350. Whenthe second table entry 344 is identical to its corresponding first tableentry 342, the SCU 302 transmits commands directly to the implanteddevice 100. However, when the second table entry 344, e.g., T_(N), isdifferent from the first table entry 342, e.g., ST_(M), the SCU 302transmits commands via an intermediary microtransponder, e.g., 100 d.The use of the translation table 340 is optional since the intermediaryaddresses can, instead, be programmed directly into a control programcontained in the program storage 310. However, it is preferable to usesuch a translation table 340 in that communications can be redirected onthe fly by just reprogramming the translation table 340 to takeadvantage of implanted transponders as required, e.g., if communicationsshould degrade and become unreliable. The translation table 340 ispreferably contained in programmable memory, e.g., RAM or EPROM, and canbe a portion of the program storage 310. While the translation table 340can be remotely programmed, e.g., via a modulated signal from theclinician's programmer 172, it is also envisioned that the SCU 302 canreprogram the translation table 340 if the communications degrade.

FIG. 7 is an exemplary block diagram showing the use of the system ofthe present invention to perform closed loop control of a body function.In block 352, the SCU 302 requests status from microsensor A (SE_(A)).The SCU 302, in block 354, then determines whether a current commandgiven to a microstimulator is satisfactory and, if necessary, determinesa new command and transmits the new command to the microstimulator A inblock 356. For example, if microsensor A (SE_(A)) is reading a voltagecorresponding to a pressure generated by the stimulation of a muscle,the SCU 302 could transmit a command to microstimulator A (ST_(A)) toadjust the sequence of drive pulses, e.g., in magnitude, duty cycle,etc., and accordingly change the voltage sensed by microsensor A(SE_(A)). Accordingly, closed loop, i.e., feedback, control isaccomplished. The characteristics of the feedback (position, integral,derivative (PID)) control are preferably program controlled by the SCU302 according to the control program contained in program storage 310.

FIG. 8 shows an exemplary injury treatable by embodiments of the presentsystem 300. In this exemplary injury, the neural pathway has beendamaged, e.g., severed, just above the patient's left elbow. The goal ofthis exemplary system is to bypass the damaged neural pathway to permitthe patient to regain control of the left hand. An SCU 302 is implantedwithin the patient's torso to control a plurality of stimulators,ST₁-ST₅, implanted proximate to the muscles respectively controlling thepatient's thumb and fingers. Additionally, microsensor 1 (SE₁) isimplanted proximate to an undamaged nerve portion where it can sense asignal generated from the patient's brain when the patient wants handclosure. Optional microsensor 2 (SE₂) is implanted in a portion of thepatient's hand where it can sense a signal corresponding tostimulation/motion of the patient's pinky finger and microsensor 3 (SE₃)is implanted and configured to measure a signal corresponding to grippressure generated when the fingers of the patient's hand are closed.Additionally, an optional microtransponder (T₁) is shown which can beused to improve the communication between the SCU 302 and the implanteddevices.

FIG. 9 shows an exemplary flow chart for the operation of the SCU 302 inassociation with the implanted devices in the exemplary system of FIG.8. In block 360, the SCU 302 interrogates microsensor 1 (SE₁) todetermine if the patient is requesting actuation of his fingers. If not,a command is transmitted in block 362 to all of the stimulators(ST₁-ST₅) to open the patient's hand, i.e., to de-energize the muscleswhich close the patient's fingers. If microsensor 1 (SE₁) senses asignal to actuate the patient's fingers, the SCU 302 determines in block364 whether the stimulators ST₁-ST₅ are currently energized, i.e.,generating a sequence of drive pulses. If not, the SCU 302 executesinstructions to energize the stimulators. In a first optional path 366,each of the stimulators are simultaneously (subject to formatting andtransmission delays) commanded to energize in block 366 a. However, thecommand signal given to each one specifies a different start delay time(using the BON parameter). Accordingly, there is a stagger between theactuation/closing of each finger.

In a second optional path 368, the microstimulators are consecutivelyenergized by a delay Δ. Thus, microstimulator 1 (ST₁) is energized inblock 368 a, a delay is executed within the SCU 302 in block 368 b, andso on for all of the microstimulators. Accordingly, paths 366 and 368perform essentially the same function. However, in path 366 theinterdevice timing is performed by the clocks within each implanteddevice 100 while in path 368, the SCU 302 is responsible for providingthe interdevice timing.

In path 370, the SCU 302 actuates a first microstimulator (ST₁) in block370 a and waits in block 370 b for its corresponding muscle to beactuated, as determined by microsensor 2 (SE₂), before actuating theremaining stimulators (ST₂-ST₅) in block 370 c. This implementationcould provide more coordinated movement in some situations.

Once the stimulators have been energized, as determined in block 364,closed loop grip pressure control is performed in blocks 372 a and 372 bby periodically reading the status of microsensor 3 (SE₃) and adjustingthe commands given to the stimulators (ST₁-ST₅) accordingly.Consequently, this exemplary system has enabled the patient to regaincontrol of his hand including coordinated motion and grip pressurecontrol of the patient's fingers.

Referring again to FIG. 3A, a magnetic sensor 186 is shown. In thecommonly assigned U.S. Pat. No. 6,185,452, it was shown that such asensor 186 could be used to disable the operation of an implanted device100, e.g., to stop the operation of such devices in an emergencysituation, in response to a DC magnetic field, preferably from anexternally positioned safety magnet 187. A further implementation isdisclosed herein. The magnetic sensor 186 can be implemented usingvarious devices. Exemplary of such devices are devices manufactured byNonvolatile Electronics, Inc. (e.g., their AA, AB, AC, AD, or AGseries), Hall effect sensors, and subminiature reed switches. Suchminiature devices are configurable to be placed within the housing ofthe disclosed SCU 302 and implantable devices 100. While essentiallypassive magnetic sensors, e.g., reed switches, are possible, theremaining devices include active circuitry that consumes power duringdetection of the DC magnetic field. Accordingly, it is preferred thatcontroller circuitry 302 periodically, e.g., once a second, providepower to the magnetic sensor 186 and sample the sensor's output signal374 during that sampling period.

In a preferred implementation of the SCU 302, the programmablecontroller 308 is a microcontroller operating under software controlwherein the software is located within the program storage 310. The SCU302 preferably includes an input 376, e.g., a non maskable interrupt(NMI), which causes a safe harbor subroutine 378, preferably locatedwithin the program storage 310, to be executed. Additionally, failure orpotential failure modes, e.g., low voltage or over temperatureconditions, can be used to cause the safe harbor subroutine 378 to beexecuted. Typically, such a subroutine could cause a sequence ofcommands to be transmitted to set each microstimulator into a safecondition for the particular patient configuration, typically disablingeach microstimulator. Alternatively, the safe harbor condition could beto set certain stimulators to generate a prescribed sequence of drivepulses. Preferably, the safe harbor subroutine 378 can be downloadedfrom an external device, e.g., the clinician's programmer 172, into theprogram storage 310, a nonvolatile storage device. Additionally, it ispreferable that, should the programmable contents of the program storagebe lost, e.g., from a power failure, a default safe harbor subroutine beused instead. This default subroutine is preferably stored innonvolatile storage that is not user programmable, e.g., ROM, that isotherwise a portion of the program storage 310. This default subroutineis preferably general purpose and typically is limited to commands thatturn off all potential stimulators.

Alternatively, such programmable safe harbor subroutines 378 can existin the implanted stimulators 100. Accordingly, a safe harbor subroutinecould be individually programmed into each microstimulator that iscustomized for the environment of that individual microstimulator and asafe harbor subroutine for the SCU 302 could then be designated thatdisables the SCU 302, i.e., causes the SCU 302 to not issue subsequentcommands to other implanted devices 100.

FIG. 10A shows a side view of a microstimulator 100 made in accordancewith the present invention which includes battery 104 for powering thecircuitry within. The battery 104 conveniently fits within a sealedelongate housing 206 (preferably hermetically sealed) which encases themicrostimulator 100. In a preferred device 100, the axial dimension 208is less than 60 mm and the lateral dimension 207 is less than 6 mm.

For the embodiment shown in FIG. 10A, the battery 104 is preferablyhoused within its own battery case 209, with the battery terminalscomprising an integral part of its case 209 (much like a conventional AAbattery). Thus, the sides and left end of the battery 104 (as orientedin FIG. 10A) may comprise one battery terminal 210, e.g., the negativebattery terminal, and the right end of the battery 104 may comprise theother battery terminal, e.g., the positive battery terminal used as theoutput terminal 128. Advantageously, because such a battery case 209 isconductive, it may serve as an electrical conductor for connecting anappropriate circuit node for the circuitry within the microstimulator100 from one side of the battery to the other. More particularly, forthe configuration shown in FIG. 10A, the battery terminal 210 may serveas a ground point or node for all of the circuitry housed within thedevice housing 206. Hence, stem 212 from the electrode 112 a on the leftend of the microstimulator 100, which from an electrical circuit pointof view is simply connected to circuit ground, may simply contact theleft end of the battery 104. Then, this same circuit ground connectionis made available near or on the rim of the battery 104 on its rightside, near one or more IC chips 216 (preferably implementing thedevice's power consuming circuitry, e.g., the controller 106 andstimulation circuitry 110) on the right side of battery 104 within theright end of the housing 206. By using the conductive case 209 of thebattery 104 in this manner, there is no need to try to pass or fit aseparate wire or other conductor around the battery 104 to electricallyconnect the circuitry on the right of the device 100 with the electrode112 a on the left side of the device 100.

FIG. 10B shows a battery powered microstimulator 100′ that issubstantially the same as the device 100 shown in FIG. 10A except thatthe microstimulator 100′ includes internal coupling capacitor 183 (usedto prevent DC current flow through the body tissue). The internalcoupling capacitor 183 is used for the embodiment shown in FIG. 10Bbecause both of the microstimulator electrodes 112 a and 112 b used bythe microstimulator 100′ are made from the same material, iridium. Incontrast, the electrodes 112 a and 112 b for the microstimulator 100shown in FIG. 10A are made from different materials, and in particularfrom iridium (electrode 112 b) and tantalum (electrode 112 a), and suchmaterials inherently provide a substantial capacitance between them,thereby preventing DC current flow. See, e.g., col. 11, lines 26-33, ofU.S. Pat. No. 5,324,316.

FIGS. 10C and 10D show two side cutaway views of the presently preferredconstruction of the sealed housing 206, the battery 104 and thecircuitry (implemented on one or more IC chips 216 to implementelectronic portions of the SCU 302) contained within. In this presentlypreferred construction, the housing 206 is comprised of an insulatingceramic tube 260 brazed onto a first end cap forming electrode 112 a viaa braze 262. At the other end of the ceramic tube 260 is a metal ring264 that is also brazed onto the ceramic tube 260. The circuitry within,i.e., a capacitor 183 (used when in a microstimulator mode), battery104, IC chips 216, and a spring 266 is attached to an opposing secondend cap forming electrode 112 b. A drop of conductive epoxy is used toglue the capacitor 183 to the end cap 112 a and is held in position byspring 266 as the glue takes hold. Preferably, the IC chips 216 aremounted on a circuit board 268 over which half circular longitudinalferrite plates 270 are attached. The coil 116 is wrapped around theferrite plates 270 and attached to IC chips 216. A getter 272, mountedsurrounding the spring 266, is preferably used to increase thehermeticity of the SCU 302 by absorbing water introduced therein. Anexemplary getter 272 absorbs 70 times its volume in water. While holdingthe circuitry and the end cap 112 b together, one can laser weld the endcap 112 b to the ring 264. Additionally, a platinum, iridium, orplatinum-iridium disk or plate 274 is preferably welded to the end capsof the SCU 302 to minimize the impedance of the connection to the bodytissue.

An exemplary battery 104 is described more fully below in connectionwith the description of FIG. 11. Preferably, the battery 104 is madefrom appropriate materials so as to provide a power capacity of at least1 microwatt-hour, preferably constructed from a battery having an energydensity of about 240 mW-Hr/cm³. A Li—I battery advantageously providessuch an energy density. Alternatively, an Li—I—Sn battery provides anenergy density up to 360 mW-Hr/cm³. Any of these batteries, or otherbatteries providing a power capacity of at least 1 microwatt-hour may beused with implanted devices of the present invention.

The battery voltage V of an exemplary battery is nominally 3.6 volts,which is more than adequate for operating the CMOS circuits preferablyused to implement the IC chip(s) 216, and/or other electronic circuitry,within the SCU 302. The battery voltage V, in general, is preferably notallowed to discharge below about 2.55 volts, or permanent damage mayresult. Similarly, the battery 104 should preferably not be charged to alevel above about 4.2 volts, or else permanent damage may result. Hence,a charging circuit 122 (discussed in the commonly assigned U.S. Pat. No.6,185,452) is used to avoid any potentially damaging discharge orovercharge.

The battery 104 may take many forms, any of which may be used so long asthe battery can be made to fit within the small volume available. Aspreviously discussed, the battery 104 may be either a primary battery ora rechargeable battery. A primary battery offers the advantage of alonger life for a given energy output but presents the disadvantage ofnot being rechargeable (which means once its energy has been used up,the implanted device no longer functions). However, for manyapplications, such as one-time-only muscle rehabilitation regimensapplied to damaged or weakened muscle tissue, the SCU 302 and/or devices100 need only be used for a short time (after which they can beexplanted and discarded, or simply left implanted as benign medicaldevices). For other applications, a rechargeable battery is clearly thepreferred type of energy choice, as the tissue stimulation provided bythe microstimulator is of a recurring nature.

The considerations relating to using a rechargeable battery as thebattery 104 of the implantable device 100 are presented, inter alia, inthe book, Rechargeable Batteries, Applications Handbook, EDN Series forDesign Engineers, Technical Marketing Staff of Gates Energy Products,Inc. (Butterworth-Heinemann 1992). The basic considerations for anyrechargeable battery relate to high energy density and long cycle life.Lithium based batteries, while historically used primarily as anonrechargeable battery, have in recent years appeared commercially asrechargeable batteries. Lithium-based batteries typically offer anenergy density of from 240 mW-Hr/cm³ to 360 mW-Hr/cm³. In general, thehigher the energy density the better, but any battery constructionexhibiting an energy density resulting in a power capacity greater than1 microwatt-hour is suitable for the present invention.

One of the more difficult hurdles facing the use of a battery 104 withinthe SCU 302 relates to the relatively small size or volume inside thehousing 206 within which the battery must be inserted. A typical SCU 302made in accordance with the present invention is no larger than about 60mm long and 8 mm in diameter, preferably no larger than 60 mm long and 6mm in diameter, and includes even smaller embodiments, e.g., 15 mm longwith an O.D. of 2.2 mm (resulting in an I.D. of about 2 mm). When oneconsiders that only about ¼ to ½ of the available volume within thedevice housing 206 is available for the battery, one begins toappreciate more fully how little volume, and thus how little batterystorage capacity, is available for the SCU 302.

FIG. 11 shows an exemplary battery 104 typical of those disclosed in thecommonly assigned U.S. Pat. No. 6,185,452. Specifically, aparallel-connected cylindrical electrode embodiment is shown where eachcylindrical electrode includes a gap or slit 242; with cylindricalelectrodes 222 and 224 on each side of the gap 242 forming a commonconnection point for tabs 244 and 246 which serve as the electricalterminals for the battery. The electrodes 222 and 224 are separated by asuitable separator layer 248. The gap 242 minimizes the flow of eddycurrents in the electrodes. For this embodiment, there are fourconcentric cylindrical electrodes 222, the outer one (largest diameter)of which may function as the battery case 234, and three concentricelectrodes 224 interleaved between the electrodes 222, with sixconcentric cylindrical separator layers 248 separating each electrode222 or 224 from the adjacent electrodes.

Accordingly, a preferred embodiment of the present invention iscomprised of an implanted SCU 302 and a plurality of implanted devices100, each of which contains its own rechargeable battery 104. As such, apatient is essentially independent of any external apparatus betweenbattery chargings (which generally occur no more often than once anhour). However, for some treatment regimen, it may be adequate to use apower supply analogous to that described in U.S. Pat. No. 5,324,316 thatonly provides power while an external AC magnetic field is beingprovided, e.g., from charger 118. Additionally, it may be desired, e.g.,from a cost standpoint, to implement the SCU 302 as an external device,e.g., within a watch-shaped housing that can be attached to a patient'swrist in a similar manner to the patient control unit 174.

The power consumption of the SCU 302 is primarily dependent upon thecircuitry implementation, preferably CMOS, the circuitry complexity andthe clock speed. For a simple system, a CMOS implemented state machinewill be sufficient to provide the required capabilities of theprogrammable controller 308. However, for more complex systems, e.g., asystem where an SCU 302 controls a large number of implanted devices 100in a closed loop manner, a microcontroller may be required. As thecomplexity of such microcontrollers increases (along with its transistorcount), so does its power consumption. Accordingly, a larger batteryhaving a capacity of 1 watt-hour is preferred. While a primary batteryis possible, it is preferable that a rechargeable battery be used. Suchlarger batteries will require a larger volume and accordingly, cannot beplaced in the injectable housing described above. However, a surgicallyimplantable device within a larger sealed housing, e.g., having at leastone dimension in excess of 1 inch, will serve this purpose when used inplace of the previously discussed injectable housing 206. FIG. 12 showsan exemplary implantable housing 380 suitable for such a device.

While embodiments with a circular cross section are presently preferred,embodiments with a non-circular cross section are also envisioned. Aswill be discussed further below, non-circular cross sections areselected from the group consisting of rectangular, triangular, oval,hexagonal, octagonal and polygon shaped. Non-circular cross sectionsallow additional manufacturing alternatives. Additionally, while it isnot believed that devices with circular cross sections will migratesignificantly after implantation, it is believed that devices withnon-circular cross sections will migrate even less and thus may allow amore precise and stable implantation near nerve or muscle tissue andthus may present additional benefits, e.g., higher sensing sensitivityor lower stimulation power and thus longer battery life betweenchargings. Alternative non-circular embodiments of the housing 206 ofmicrostimulator 100, contemplated by the present invention, are shown inFIGS. 13-24. More specifically, FIG. 13 shows a schematic representationof housing 206′, having a square cross-section (see FIG. 14) withoutexpressly showing the inclusion of the internal elements of themicrostimulator 100. It is to be understood that operation of themicrostimulator 100, including the electrode structure for contact withbody tissue, is configured and functions in accordance with theinvention described herein independent of the shape of the housing 206,and thus need not be repeated for each housing shape embodiment. Thelengthwise dimension 456 may be greater than 60 mm, e.g., in the rangeof about 60 mm to 70 mm, and the lateral dimension 458 may be greaterthan 6 mm, e.g., in the range of about 6 mm to 7 mm. The lengthwisedimension 456 and the lateral dimension 458 are preferably selected fromthe following dimensional groupings: a) lengthwise dimension 456 beingless than 60 mm and lateral dimension 458 being greater than or equal to6 mm; b) lengthwise dimension 456 being greater than 60 mm and lateraldimension 458 being less than or equal to 6 mm; and c) lengthwisedimension 456 being less than or equal to 60 mm and lateral dimension458 being less than or equal to 6 mm.

With reference to FIG. 15 and the cross-sectional view of FIG. 16, thereis shown yet another housing embodiment 206″. The housing 206″ isrectangular in cross-section having a lengthwise dimension 260 which maybe greater than 60 mm and preferably is in the range of 60 mm to 70 mm.A lateral dimension 462 may be greater than 6 mm and preferably is inthe range of 6 mm to 7 mm. The lengthwise dimension 460 and the majorlateral dimension 462 are preferably selected from the followingdimensional groupings: d) lengthwise dimension 460 being less than 60 mmand major lateral dimension 462 being greater than or equal to 6 mm; e)lengthwise dimension 460 being greater than 60 mm and major lateraldimension 462 being less than or equal to 6 mm; and f) lengthwisedimension 460 being less than or equal to 60 mm and major lateraldimension 462 being less than or equal to 6 mm. Similarly, minor lateraldimension 464 may be less than or greater than 6 mm and preferably is inthe range of 6 mm to 7 mm.

With reference to FIG. 17 and the cross-sectional view of FIG. 18, thereis shown still yet another housing embodiment 206′″. The housing 206′″is triangular in cross-section having a lengthwise dimension 466 whichmay be greater than 60 mm and preferably is in the range of 60 mm to 70mm and a lateral dimension 468 which may be greater than 6 mm andpreferably in the range of 6 mm to 7 mm. The lengthwise dimension 466and the lateral dimension 468 are preferably selected from the followingdimensional groupings: g) lengthwise dimension 466 being less than 60 mmand lateral dimension 468 being greater than or equal to 6 mm; h)lengthwise dimension 466 being greater than 60 mm and lateral dimension468 being less than or equal to 6 mm; and i) lengthwise dimension 466being less than or equal to 60 mm and lateral dimension 468 being lessthan or equal to 6 mm.

With reference to FIG. 19 and the cross-sectional view of FIG. 20, thereis shown a still further housing embodiment 206″″. The housing 206″41 isoval in cross-section having a lengthwise dimension 470 which may begreater than 60 mm and preferably is in the range of 60 mm to 70 mm anda major lateral dimension 472 which may be greater than 6 mm andpreferably is in the range of about 6 mm to 7 mm and minor lateraldimension 474 of about 6 mm and preferably is in the range of about 6 mmto 7 mm. The lengthwise dimension 470 and the major lateral dimension472 are preferably selected from the following dimensional groupings: j)lengthwise dimension 470 being less than 60 mm and major lateraldimension 472 being greater than or equal to 6 mm; k) lengthwisedimension 470 being greater than 60 mm and major lateral dimension 472being less than or equal to 6 mm; and l) lengthwise dimension 470 beingless than or equal to 60 mm and major lateral dimension 472 being lessthan or equal to 6 mm.

With reference to FIG. 21 and the cross-sectional view of FIG. 22, thereis shown a further housing embodiment 206″″′. The housing 206″″′ ishexagonal in cross-section having a lengthwise dimension 476 which maybe greater than 60 mm and preferably is in the range of 60 mm to 70 mm,a major lateral dimension 478 which may be greater than 6 mm andpreferably is in the range of 6 mm to 7 mm and a minor lateral dimension480 of about 6 mm and preferably is in the range of about 6 mm to 7 mm.The lengthwise dimension 476 and the major lateral dimension 478 arepreferably selected from the following dimensional groupings: m)lengthwise dimension 476 being less than 60 mm and major lateraldimension 478 being greater than or equal to 6 mm; n) lengthwisedimension 476 being greater than 60 mm and major lateral dimension 478being less than or equal to 6 mm; and o) lengthwise dimension 476 beingless than or equal to 60 mm and major lateral dimension 478 being lessthan or equal to 6 mm.

With reference to FIG. 23 and the cross-sectional view of FIG. 24, thereis shown a still further housing embodiment 206″″″. The housing 206″″″is octagonal in cross-section having a lengthwise dimension 482 whichmay be greater than 60 mm and preferably is in the range of 60 mm to 70mm, a major lateral dimension 484 which may be greater than 6 mm andpreferably is in the range of 6 mm to 7 mm, and a minor lateraldimension 486 of about 6 mm and preferably is in the range of about 6 mmto 7 mm. The lengthwise dimension 482 and the major lateral dimension484 are preferably selected from the following dimensional groupings: p)lengthwise dimension 482 being less than 60 mm and major lateraldimension 484 being greater than or equal to 6 mm; q) lengthwisedimension 482 being greater than 60 mm and major lateral dimension 484being less than or equal to 6 mm; and r) lengthwise dimension 482 beingless than or equal to 60 mm and major lateral dimension 484 being lessthan or equal to 6 mm.

Preferably, as identified in FIGS. 14, 16, 18, 20, 22, and 24, thehousing wall thickness T (290) is in the range of about 1 mm to 4 mm.Moreover, although the cross-sectional views of the housings of FIGS.14, 16, 18, 20, 22, and 24 appear to have sharp corners, it is to beunderstood that rounded corners are also contemplated by the invention.As can be appreciated, rounded corners for the housing, facilitatemanufacture of the housing as well as the implantation of themicrostimulator 100. The dimensional groupings for the housing aspresented above provide significant flexibility in configuring themicrostimulator 100 to house alternative arrangements of themicrostimulator's internal and external electrical and/or mechanicalparts.

While various implantable devices have been shown and described havingcylindrical and non-cylindrical cross sections, it is to be understoodthat other polygon shaped cross sections that have not been specificallymentioned are also considered to be within the scope of the presentinvention. For example, various polygon shaped cross sections have beenspecifically shown, i.e., triangular (3 sided), rectangular (4 sided),hexagonal (6 sided), and octagonal (8 sided) shapes have been alreadyshown and described but other polygon shaped cross sections are alsoconsidered to be within the scope of the present invention, e.g.,pentagonal (5 sided), 7 sided, and 9 or more sided polygons.Additionally, while not expressly discussed so far, it is to berecognized by one of ordinary skill in the art that the inner crosssectional shape of the insertion tool 176 is preferably altered toaccommodate devices with non-cylindrical cross sections, e.g., a squareshape for a square shaped device, triangular shaped for a triangularshaped device, etc.

FIGS. 25-34 are directed to a placement structure 500 that is useful forplacing and retaining one of the aforementioned implantable devices 100in close proximity to a nerve, muscle tissue, or the like, i.e.,neural/muscular tissue. For the purposes of this applicationneural/muscular tissue is understood to signify tissue that passes orresponds to neural signals which includes nerve fibers or muscle tissueor any combination thereof. This structure 500 may present additionalbenefits, e.g., higher sensing sensitivity or lower stimulation powerand thus longer battery life between chargings. The placement structure500 is preferably comprised of two main portions: (1) a holder 502 forholding and retaining the implantable device 100 within and (2) one ormore sets (e.g., pairs) of wings 504 for capturing neural/musculartissue. Preferably, the placement structure 500 is primarily formed fromof-a biocompatible plastic, e.g., SILASTIC®, a registered trademark ofDow Corning, that is elastic and is also an electrical insulator. In anexemplary embodiment, the holder 502 is essentially semi-circular incross section and has a hollow cavity 506 having end plates 508 and 510that essentially conforms to the size and shape of implantable device100 such that the implantable device 100 may be snapped into the cavity506 and is held by the elasticity of the holder 502 (see FIGS. 25 and 26which show the insertion of the implantable device 100 into the cavity506 of the holder 502 of the placement structure 500. It should be notedthat while the exemplary capture device 500 is shown for holding animplantable device 100 having a circular cross section, it should bereadily apparent to one of ordinary skill in the art that this exemplarystructure is readily alterable to accommodate devices havingnon-circular cross sections as well.

With the implantable device 100 within the cavity 506, the placementstructure 500 may be placed in contact, e.g., snapped around, withneural/muscular 512 tissue using the elasticity of the wings 504 tocapture/grab the neural/muscular tissue 512 (see FIG. 27, also see thecross sectional view of FIG. 32). As noted in FIGS. 28 and 29, preferredembodiments include structures that rely upon the elasticity of thewings 504 to capture/grab the neural/muscular tissue (see FIG. 28) aswell as structures that include hook elements 514 that furthersupplement the elasticity of the wings 504 for capturing/grabbing theneural/muscular tissue 512.

While a cut-down procedure may be used, it is preferred that implantabledevice 100 within the placement structure 500 be inserted with ahypodermic type insertion tool, e.g., an adapted laparoscopic device 516(see FIG. 30 and U.S. Pat. No. 6,582,441 which is incorporated herein byreference). In preparation for implantation, the wings 504 of theplacement structure 500 are preferably folded inward in proximity to theimplantable device 100 within holder 502 and the combination is insertedwithin the laparoscopic device 516 (see FIG. 31). The laparoscopicdevice 516 is then inserted as is known in the art into the patientuntil the tip 518 of laparoscopic device 516 approaches the desiredinsertion point of the neural/muscular tissue. Upon reaching its desiredinsertion point, the placement structure 500 is ejected from thelaparoscopic device 516 (or conversely and equivalently, thelaparoscopic device 516 is withdrawn while the placement structure 500is held at the desired insertion point) and the wings 504 elasticallyextend to their nominal position (see FIG. 28) where they are suitablefor capturing the neural/muscular tissue 512.

In a first preferred embodiment 500′ (see FIG. 27), the electrodes 112of the implantable device 100 directly make contact with theneural/muscular tissue 512 at electrode/tissue contact points 520 and522 (for the exemplary two electrode implantable device 100).Accordingly, the initial depolarization (or sensing) associated with theimplantable device 100 extends axially along the neural/muscular tissue512.

In a second preferred embodiment 500″ (see FIG. 33), the wings 504 and aportion of the cavity 506 include conductive layers 524, 526 (preferablycomprised of a plurality of discrete conductive paths, e.g., combshaped, slotted, or formed of serpentine paths, to reduce eddy currentsand heat build up associated with the receipt of RF fields duringcharging). Accordingly (again referring to FIG. 32), the conductivelayer 524 now additionally makes contact with at contact surfaces 528and 530 (in addition to contact point 520) and thus there are now threecontact point areas associated with each electrode 112 and thus currentflow within the neural/muscular tissue 512 may be increased withoutincreasing the compliance voltage since there will now be a lowerresistance between the electrodes 112 and the neural/muscular tissue512.

In a third preferred embodiment 500′″ (see FIG. 34), the initialdepolarization (or sensing) is applied transversely to theneural/muscular tissue 512 through a single pair of wings 504. In thisembodiment, the distal end 532 of the capture device 500′″ is a boottype structure 534 that is suitable for capturing distal electrode 112 bof the implantable device 100. Within the boot type structure 534, aconductive layer 536 (preferably a plurality of paths, e.g., slotted, toreduce eddy circuits, as previously described) electrically connect thedistal electrode 112 b of the implantable device 100 along pathway 538to first proximal wing 504′ at the proximal end 540 of the capturedevice 500′″. Preferably, wing 504′ is longer/wider than the proximalelectrode 112 a so that electrical pathway 538 and its associatedconductive layers 536 and 542 do not make contact with the proximalelectrode 112 a. Conductive layer 546 extends from within the cavity 506at the proximal end 540 to the inner surface of second proximal wing504″. Accordingly, once inserted, the distal electrode 112 b iselectrically coupled to first proximal wing 504′ and the proximalelectrode 112 a is electrically coupled to the second proximal wing504″. Once the placement structure 500′″ is used to capture theneural/muscular tissue 512, stimulation vectors 548 and 550 are appliedtransversely to the tissue 512 (see FIG. 32). Alternatively, theelectrical pathways associated with second proximal wing 504″ may beomitted, in which case only stimulation vector 550 is present. (Note,the polarity of the stimulation vector is only shown for exemplarypurposes and may be reversed as needed. Furthermore, the use of the termstimulation vector is equally applicable to describe the vector forsensing a neural/muscular signal, i.e., a sensor or stimulation/sensorvector.)

In the third preferred embodiment 500′″, the implantable device 100 isinserted into the capture device 500′″ by first inserting the distalend, i.e., electrode 112 b, of the implantable device 100 into the boottype structure 534 of the placement structure 500′″ and then pressingthe proximal end, i.e., electrode 112 a, of the implantable device 100into the proximal end 540 of the placement structure 500′″. This differsfrom the other two embodiments where both ends of the implantable device100 are preferably inserted concurrently into the placement structure.

Notably, in the third preferred embodiment, there is only one set ofwings, i.e., first and second proximal wings 504′ and 504″. Accordingly,during implantation, only a single pair of wings need to capture theneural/muscular tissue 512 and thus implantation is simplified.

FIG. 35 is an alternative embodiment 500′″ of the placement structure ofFIG. 25 and the implantable medical device of FIGS. 10A-10D wherein theimplantable medical device 100″ additionally includes a plurality ofstimulator/sensor circuitry portions 560 (e.g., 560 a-560 n) that arecoupled to inner portions of the wings 504 via electrode connectors 562,564 on the outer surface of the implantable medical device 100″ and thecavity of the placement structure 500′″ includes a plurality ofconductive paths to provide electrical coupling between the electrodeconnectors 562, 564 of the implantable device 100″ to electrodes 567,569 within the wings 504 for coupling to displaced portions of theneural/muscular tissue. In this embodiment, the implantable medicaldevice 100″ includes a plurality of stimulator/sensor circuitry portions560 each of which includes the capabilities of the aforementionedstimulator circuitry 110 and/or sensor circuitry 188 described inreference to FIG. 3A. Accordingly, when used with a plurality ofstimulator circuitry portions 560, each portion may be stimulated withdifferent current intensities and/or timing and thereby steer thestimulation pulses to a desired portion (foci) of the neural/musculartissue. Alternatively or additionally, a plurality of sensor circuitryportions 560 may be used to sense neural/muscular responses fromdifferent portions of the neural/muscular tissue, e.g., to sense evokedresponses or discrete neural/muscular signals.

To facilitate use of these functions, the implantable medical device100″ may include a plurality of electrode connectors (preferablysemicircular rings) 562, 564 which are coupled to the stimulator/sensorcircuitry portions 560. Lower portions of these rings 562, 564 arerespectively coupled to the placement structure 500′″ when theimplantable medical device 100″ is located within the placementstructure 500′″ to contact electrical pathways 566, 568. Upper portionsof these rings/electrodes 562, 564 may make direct contact with theneural/muscular tissue after implantation. These functions may befurther facilitated by the placement of electrodes 567, 569 within thewings 504 that have displaced locations within the wings and, inoperation, are distributed around the neural/muscular tissue.Preferably, upper portions of the electrical pathways that wouldotherwise contact the neural/muscular tissue are coated with aninsulation layer 570 (not shown) with the exception of the portionscorresponding to electrodes 567, 569 to allow the electrodes 567, 569 toperform current steering.

FIG. 36 shows an alternative implementation of that which wasfunctionally described in relation to FIG. 35. However, in thisimplementation a single, essentially U-shaped, structure 600 havingelastic wings 504 is integrally formed which encompasses thefunctionality of the implantable medical device 100″ contained withinthe placement structure 500′″. In this single integral structure 600, aplurality of electrodes 602, 604, 606 (e.g., 602 a-602 n, 604 a-604 n,606 a-606 n) are distributed (and preferably individually driven bycircuitry portions 560 contained within the U-shaped structure 600 alongwith other circuitry as described in reference to FIG. 3A) within theinner U-shaped cavity 608 of structure 600.

FIG. 37 shows a next alternative implementation of an integral device650 similar to that shown in FIG. 36 to the extent that it too is anintegral device but in this case it has its elastic wings 504 formedfrom a silicone rubber impregnated cloth that is permanently attached tothe functional equivalent of the implantable medical device 100″described in reference to FIG. 35. In most other aspects, thisembodiment is functionally equivalent to that which has been previouslydescribed.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention. For example, while notexpressly shown, the hook portions shown and described in reference toFIG. 29 are equally applicable to the embodiments of FIGS. 36 and 37. Itis therefore to be understood that within the scope of the claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A method for facilitating placement of an implantable device havingat least two electrodes proximate to neural/muscular tissue using aplacement structure comprised of a holder having a hollow cavity formedwithin for holding and retaining the implantable device within and atleast one set of elastic wings for capturing neural/muscular tissue,said method comprising the steps of: snapping the implantable devicewithin the holder portion of the placement structure; folding theelastic wings inward toward the implantable device within the holderportion; inserting the placement structure with inwardly folded wingswithin the hollow portion of a laparoscopic type insertion device;placing the distal end of the laparoscopic type insertion deviceproximate to a desired neural/muscular pathway; ejecting the placementstructure from the distal end of the laparoscopic type insertion device;capturing the desired neural/muscular pathway with the unfolded elasticwings; and removing the laparoscopic type insertion device.